1. Field of the Invention
The present invention relates to improvements in a printing system of an ink jet printer and an ink selecting method, and more particularly to an improvement to attain an excellently printing quality.
2. Description of the Related Art
Recently, in association with the popularization of a personal computer, a printer as a data output apparatus, especially, a printer based on an ink jet type has been extremely technically advanced. The products having various uses and features, such as an product that is proud of photographic quality, an product that carries out a printing operation at a high speed similar to that of a laser printer, and the like, are on the market.
The printer based on the ink jet type usually includes color inks having a plurality of colors and black ink of a single color. Thus, color image can be printed in addition to a printing operation of a single color character.
In recent years, the desire of the usage of the ink jet type printer not only for a personal use but also for an office work has been increased as the change in needs of a user. Thus, the necessity of printing on a large scale requires not only the printing of a high speed but also the sharpness of a character similar to that of the laser printer, and the printing adaptability on a plain paper.
The printer based on the ink jet type uses liquid ink as a recording agent, different from the laser printer. Thus, the printing quality is liable to be influenced by the absorption property of a printed material (a recording paper). That is, the so-called feathering in which the permeation of ink along a paper fiber causes the ink to be extended from an image boundary in a shape of beard occurs on a plain paper where permeation of ink is not particularly controlled. Hence, this result in a problem in a business application in which the character printing quality is considered to be important.
As a means to solve those various problems, a glossy paper for ink jet is already known in which improvement is made to the recording paper as a material to be printed. If this glossy paper is used, it is possible to carry out the printing operation having little feathering. However, the glossy paper is typically expensive over the plain paper. Thus, if it is used for the business work in which a large number of papers are used, it is disadvantageous in view of a running cost. For this reason, it is desired to attain the improvement for the sake of the printing operation of the plain paper from the side of the ink.
When the ink for the ink jet is roughly classified from the viewpoint of the permeability to a paper, it is roughly classified into two types, namely, a permeability type and a non-permeable type.
In order to avoid the above-mentioned feathering, typically, an addition rate of permeation agent to be added to the ink is reduced and the surface tension of the ink is increased so that the ink is hard to be permeated. However, if it is excessively non-permeant, a diameter of an ink drop (hereafter, referred to as [Dot Diameter]) is reduced after the ink drop is hit on the paper and dried. Then, at a time of solid patch of full duty (perfect paint-out), especially in a case of a lower resolution mode, a portion on which the ink is not deposited is generated between ink dots (hereafter, referred to as [Portion Between Dots]). Thus, this may result in a problem that a sufficient image density can not be obtained.
In order to obtain the excellent printing quality on the plain paper, it is especially necessary to reserve the sufficient image density in the solid image and the character printing quality at the same time. However, since they have the relation of mutual trade-off, it is difficult to attain both of them. Thus, actually, it is typically done to repeatedly carry out a series of cycles, such as
(1) the trial production of ink
(2) the printing operation
(3) the evaluation of the image density and the character printing quality
(4) the trial production of ink
to test various types of inks and accordingly determine the composition of the ink.
This results in problems that a long time is always required to develop the ink and that a collection of a development cost causes an entire cost of an ink jet apparatus to be increased, and so on.
It is therefore an object of the present invention to provide a printing system of an ink jet printer, which can solve the above-mentioned problems of the conventional technique and suppress the feathering and obtain a sufficient image density, and also provide an ink selecting method of an ink jet printer, which can easily select ink suitable for the ink jet printer and a recording paper.
The present invention is a printing system of an ink jet printer which discharges an ink from the ink jet head and carries out a printing operation while relatively shifting an ink jet head and a recording paper in two shifting directions orthogonal to each other. In order to attain the above-mentioned object, it is especially designed such that when a resolution in any one shifting direction of the two shifting directions is assumed to be xe2x80x9caxe2x80x9d and a resolution in the other shifting direction orthogonal to the one shifting direction is assumed to be xe2x80x9cbxe2x80x9d and when the ink jet head is driven to draw a straight line having no overlap of dots in the other shifting direction along the one shifting direction, a property of the ink is adjusted on the basis of the resolution xe2x80x9caxe2x80x9d, the resolution xe2x80x9cbxe2x80x9d and a property of the recording paper, in such a way that a line width xe2x80x9cxxe2x80x9d of this straight line is x=(a2+b2)xc2xd and a TEP value is 10 or less.
The property of the ink is adjusted correspondingly to the resolutions xe2x80x9caxe2x80x9d, xe2x80x9cbxe2x80x9d and the property of the recording paper so that the line width xe2x80x9cxxe2x80x9d when the straight line having no overlap of the dots is drawn is x=(a2+b2)xc2xd. Thus, the sufficient image density can be obtained even in the solid patch (perfect paint-over) of the full duty. Also, the property of the ink is adjusted correspondingly to the property of the recording paper so that the TEP value of this straight line is 10 or less. Thus, the occurrence of the feathering is prevented. Hence, the usage of the ink satisfying those two conditions enables the feathering to be suppressed, and thereby enables the sufficient image density to be obtained.
Here, there is no special limitation on the colorant included in the ink. However, the most suitable colorant is pigment.
This is because the pigment ink is insoluble in solvent and it is dispersed, and the permeation is hard to be induced as compared with dye ink, and it is advantageous from the viewpoint of the feathering prevention.
Also, in a case of a business application in which a large number of recording papers are consumed, the property of the ink is desired to be adjusted so as to satisfy the conditions of x=(a2+b2)xc2xd and the TEP value of 10 or less when printing on a plain paper.
The property of the ink is adjusted so as to be optimal for the plain paper. Thus, printing on a large scale can be carried out at a low cost.
In particular, those conditions are effective if they are applied to the ink of a carbon black in which a printing operation is carried out at a single color.
This is because the occurrence of the feathering and the lack of the image density are outstanding in the case of the carbon black print in which the single color is printed only once, as compared with the case of the color print in which a printing operation is carried out while a plurality of colors overlap each other.
A piezoelectric element can be used as a driving source for discharging the ink from the ink jet head.
An ink jet printer is well known which is designed so as to be able to select a resolution. Here, a maximum resolution of the ink jet printer is determined by a hardware configuration such as characteristic of stepping motor for relatively shifting the ink jet head and recording paper. And selectable resolutions are determined based on a minimum shifting amount calculated by the maximum resolution. That is, if the maximum resolution is 1200 dpi (dot/inch), it is possible to select 1200 dpi (minimum shifting amount) 600 dpi (double of minimum shifting amount), 400 dpi (triple of minimum shifting amount) and 300 dpi (quadruple of minimum shifting amount), respectively. These resolutions are integer multiple of the minimum shifting amount by defining as the maximum resolution peculiar to an ink jet printer. In the case of the ink jet printer having such design, a driving timing and a driving time of the piezoelectric element are controlled correspondingly to the selected resolution at the time of the printing. Thus, if the property of the ink is adjusted so as to attain the above-mentioned two conditions for any one resolution defined as a reference, the two conditions can be attained also for the other resolutions.
Moreover, it is also possible to apply present invention to the configuration of a so-called bubble jet, in which the ink is heated to thereby drive the ink jet head and accordingly discharge the ink.
Also in this case, the heating timing and the heating time are controlled correspondingly to the selected resolution in the printing operation. Thus, if the property of the ink is adjusted so as to attain the above-mentioned two conditions for any one resolution defined as the reference, the two conditions can be attained also for the other resolutions.
In a case of an ink jet printer that does not carry out the special ink discharge control based on the resolution although the resolution can be selected in the printing operation, the property of the ink is adjusted so as to insure the two conditions in the situation that the roughest resolution is selected to carry out the printing operation, in order to reserve the sufficient image density even if the roughest resolution is selected to carry out the printing operation. For example, in the case that the resolution can be selected from 1200 dpi, 600 dpi, 400 dpi and 300 dpi, the property of the ink is desired to be adjusted so as to satisfy the two conditions even if the printing operation of 300 dpi is done.
However, xe2x80x9cRoughest Resolutionxe2x80x9d in this explanation does not include the resolution corresponding to a draft mode (an extremely rough line image used only to check a printing state and the like). In the rough printing used only to check the printing state, the function of perfectly painting out the solid patch portion is not originally required, and there is no meaning in the complementation for the portion between the dots. Also, if the size of the ink dot is adjusted so as to attain the image density in the solid patch portion at the draft mode, a trouble is brought about in the precise printing and drawing at the high resolution.
An ink selecting method according to the present invention is an ink selecting method of an ink jet printer, which discharges an ink from the ink jet head, and then carries out a printing operation while relatively shifting an ink jet head and a recording paper in two shifting directions orthogonal to each other. In order to attain the above-mentioned object, it is designed such that a resolution in any one shifting direction of the two shifting directions is assumed to be xe2x80x9caxe2x80x9d, and a resolution in the other shifting direction orthogonal to the one shifting direction is assumed to be xe2x80x9cbxe2x80x9d, and an operation for driving the ink jet head and then drawing a straight line having no overlap of dots in the other shifting direction along the one shifting direction is repeatedly executed while different kind of ink is applied each time. Then, a line width xe2x80x9cxxe2x80x9d of the straight line is measured for each execution, and the ink satisfying a condition that this line width xe2x80x9cxxe2x80x9d is x=(a2+b2)xc2xd and a TEP value of this straight line is 10 or less is selected as the ink suitable for the ink jet head and the recording paper.
As mentioned above, the straight line having no overlap of the dots is drawn. Then, the allowance or rejection of the ink is judged only on the basis of the TEP value and the line width xe2x80x9cxxe2x80x9d of the straight line. Thus, the process required to judge the allowance or rejection of the ink is largely simplified as compared with the conventional ink selecting method of actually printing the character and the solid image and then judging the allowance or rejection of the ink. Hence, the total time and labor cost are reduced which are required to develop and select the ink. Moreover, the reduction in a development cost leads to the reduction in a manufacturing cost of an apparatus.
Also, when such an ink selecting method is applied, it is desired that in the two shifting directions, the shifting direction superior in the straightly shifting accuracy and the resolution is defined as the one shifting direction, and the remaining other shifting direction is defined as the other shifting direction.
In the situation that the feeding operation is stopped in the shifting direction which is relatively inferior in the straightly shifting accuracy and the resolution (the positioning accuracy), the feeding operation is performed only on the shifting direction superior in the straightly shifting accuracy and the resolution, and the straight line is drawn. Thus, the evaluation of the TEP value with regard to the feathering is made further accurate. (The TEP value is evaluated on the basis of the deviation in a distance between an ideal boarder line and an actually drawn image boundary. Hence, the proper evaluation can be attained in that having the higher accuracy of the actually drawn straight line).